The present invention is directed to compound archery bows, and more particularly to a so-called single-cam compound archery bow having a power let-off cam mounted on the end of only one of the bow limbs.
Compound archery bows typically are of the so-called dual-cam design, originated in U.S. Pat. No. 3,486,495. Bows of this type typically comprise a bow handle having limbs mounted on and extending from opposed ends of the handle. Power let-off cams are rotatably mounted on the free ends of the bow limbs, and are interconnected by one or more cable sections including a draw string section. As the bow draw string is drawn away from the handle, draw force initially increases as the limbs are drawn together and the cams rotate to a power let-off point, and thereafter the leverage increases and the draw force decreases as the cams rotate further but with little additional limb flexure. This so-called compound action allows full bow draw to be maintained at lesser force without fatigue to the archer. A problem inherent in dual-cam bows of this type lies in the fact that the cams must be closely matched and synchronized with each other in order to insure straight-line (or substantially straight-line) travel of the nock point on the bowstring, and the limbs must be closely balanced and evenly stressed as the string is drawn. Damage to or mismatch of the cams, mismatch or incorrect adjustment of the limbs, or stretching of the cable sections can cause loss of synchronization between the cams and uneven stressing of the limbs, resulting in less than optimum performance of the bow and erratic arrow flight.
In order to overcome the aforementioned deficiencies of dual-cam bows, it has heretofore been proposed to provide a compound bow that has a single power let-off cam disposed at the end of one bow limb, and a control pulley or wheel disposed at the end of the opposing limb over which the bowstring is trained. U.S. Pat. No. 5,505,185 discloses such a single-cam compound bow. A control cable cooperates with a power let-off cam and a control groove in the control wheel or a second let-out groove on the power cam to maintain the desired relationship or timing between bowstring let-out grooves in the control wheel and power cam.
In this way, identical or substantially identical incremental bowstring cable travel to and from the bowstring let-out grooves is obtained, thereby yielding straight-line nock travel as the bowstring cable is drawn and released. A power cable extends from the power cam to the opposing bow limb for flexing the blow limbs uniformly as the bowstring is drawn, and for cooperating with the power cam to obtain the power let-off action that is characteristic of compound bows.
Although the single-cam compound bow disclosed in the noted patent addresses and overcomes many problems theretofore extant in the art, further improvements remain desirable. In particular, the noted patent does not disclose any means or technique for adjusting draw length of the bow. That is, the bow disclosed in the noted patent obtains straight-line nock travel for a given bow draw length for which the power cam and the control wheel or the second let-out groove of the power cam are designed. In order to change or adjust bowstring draw length, the power cam and/or the control wheel must be changed to accommodate the new desired draw length while maintaining synchronous timing between the cam and wheel. In a commercial single-cam compound bow of a different design, accommodation is made for changing the bowstring cable anchor point at the power let-off cam, and thereby changing the bowstring draw length. However, since the cams and wheels are optimized for only a single draw length, changing the bowstring anchor point inherently changes the path of nock travel as the bow is drawn and released, and consequently affects shootability of the bow.
U.S. Pat. No. 5,934,265 discloses a single-cam compound archery bow that includes a bow handle from which bow limbs project, a control wheel rotatably mounted on one end of one limb and a power cam rotatably mounted at an opposing end of the other limb. A power cable segment is anchored at one end to the one limb and at a second end to the power cam at a position to wrap into and unwrap from a power cable groove on the power cam. A bowstring cable segment is anchored to the control wheel and to the power cam at positions to wrap into and unwrap from first and second bowstring let-out grooves on the control wheel and the power cam respectively. The bowstring cable segment has a nock point disposed between the spaced limb ends. A control cable segment is anchored at one end to the control wheel at a position to wrap into and unwrap from a control groove on the control wheel, and is anchored at an opposing end to the power cam. As the bowstring cable segment is drawn away from the handle, the bowstring cable segment unwraps equally from the control wheel and power cam, wraps the power cable segment into the power cable groove on the power cam so as to draw the bow limb ends together to a power let-off point at the power cable groove, and wraps the control cable segment into the control groove on the control wheel. Length of the power cable groove on the power cam, and position of the power let-off point on the power cam, are adjustable while maintaining a fixed separation between the power let-off point and the control cable anchor on the power cam, so that the nock point travels in a straight line as the bowstring cable section is drawn and released independent of adjusted length of the power cable groove and position of the power let-off point. U.S. Pat. No. 6,082,347 discloses a single-cam compound archery bow in which, in the preferred embodiments, provision is made at both the power cam and the control wheel for adjusting bowstring cable draw length. Furthermore, timing indicia are provided on both the power cam and the control wheel for selective registry with the control cable segment on the control wheel and the power cable segment on the power cam to fine-tune adjustment of nock point travel.